Oh wow.
I've never seen so much self-delusion in a guy since I was acting this way myself.
That was back in '09, and it was a situation analogous to your own.
These types of chicks are not unique, they are prolific: they are pretty and sexy and cute. They are slvts. They are attention wh0res. They have few if any female friends. 5~8 male friends. You don't know this at the moment, but she fvcks those male "friends" regularly, ALL of them.
You think you're "#3". HAH! Even if you're number 1 flavour of the month, know this: she hasn't dropped her other boy "friends", and she never will. NEVER. You can NEVER win. You can NEVER make her "your" girl.
Because in her mind she has needs that cannot be met by merely one guy alone. She is entitled; she needs the security of a rich guy to be her beta provider. She needs the excitement of an alpha sex god to be her lover. She needs a model-looking hunk trophy bf to validate to herself/her friends. She needs the friendship of a family friend to keep her connected to that part of her life. Etc etc etc. And she has no qualms about sleeping with ALL of these people, which is something that she will CERTAINLY continue to do, no matter what. (and yes, she needs her exotic foreign lover as well, the one who's d1ck she hasn't stopped longing for all the while she's been hanging out with you...)
You don't want to believe me, but I have lived wisdom and experience that cannot be contradicted.
She of course certainly has strong feelings for you. But she can't be exclusive to you, she NEVER will be exclusive to you. Should you make the mistake of trying to force her to be exclusive to you, ever, she may well pretend to be so, and use you for your money.
But without a SHADOW of a doubt, she will continue to fcuk other men, and she always will, until at least age 40, if not until the day that she dies.
She may well want you to become her boyfriend, but she will not want to be your girlfriend, at least not a proper girlfriend in the accepted sense of the word, if you know what I mean, and that is a very pathetic situation for a man to be in.
This is a reality check man, and I have no doubt you'll try and ignore it and overthink and over rationalise it and end up blundering head first into disaster anyway. You're under the powerful influence of hormones and it is leading you into disaster.
So, if I can only give you some advice which I think there is a chance you might follow, it is this: under NO circumstances stop dating and f#cking other girls.
You will want to. You will want to promise exclusivity with her, even though she is constitutionally incapable of being exclusive to you.
DON'T DO IT.
F#ck as many other girls as you can, and start dating hotter girls than you were previously. Much hotter.
Look, I know she's sweet and you have a connection and you're so compatible and its special and every thing.
But guess what, she shares special relationships with between 5~8 other guys as well, she's compatible with all of those other guys in certain ways as well. She maintains intense, intimate communication with all of those guys as well.
I've been in this situation man. It doesn't work out like a fairy tale, trust me.